Elevation of serum pyruvate kinase M2 (PKM2) in IBD and its relationship to IBD indices

Targeting pyruvate kinase M2 for the treatment of kidney disease

Pyruvate kinase M2 (PKM2), a rate limiting enzyme in glycolysis, is a cellular regulator that has received extensive attention and regards as a metabolic regulator of cellular metabolism and energy. Kidney is a highly metabolically active organ, and glycolysis is the important energy resource for kidney. The accumulated evidences indicates that the enzymatic activity of PKM2 is disturbed in kidney disease progression and treatment, especially diabetic kidney disease and acute kidney injury. Modulating PKM2 post-translational modification determines its enzymatic activity and nuclear translocation that serves as an important interventional approach to regulate PKM2. Emerging evidences show that PKM2 and its post-translational modification participate in kidney disease progression and treatment through modulating metabolism regulation, podocyte injury, fibroblast activation and proliferation, macrophage polarization, and T cell regulation. Interestingly, PKM2 activators (TEPP-46, DASA-58, mitapivat, and TP-1454) and PKM2 inhibitors (shikonin, alkannin, compound 3k and compound 3h) have exhibited potential therapeutic property in kidney disease, which indicates the pleiotropic effects of PKM2 in kidney. In the future, the deep investigation of PKM2 pleiotropic effects in kidney is urgently needed to determine the therapeutic effect of PKM2 activator/inhibitor to benefit patients. The information in this review highlights that PKM2 functions as a potential biomarker and therapeutic target for kidney diseases.

Exploring the diverse role of pyruvate kinase M2 in cancer: Navigating beyond glycolysis and the Warburg effect

Pyruvate Kinase M2, a key enzyme in glycolysis, has garnered significant attention in cancer research due to its pivotal role in the metabolic reprogramming of cancer cells. Originally identified for its association with the Warburg effect, PKM2 has emerged as a multifaceted player in cancer biology. The functioning of PKM2 is intricately regulated at multiple levels, including controlling the gene expression via various transcription factors and non-coding RNAs, as well as adding post-translational modifications that confer distinct functions to the protein. Here, we explore the diverse functions of PKM2, encompassing newly emerging roles in non-glycolytic metabolic regulation, immunomodulation, inflammation, DNA repair and mRNA processing, beyond its canonical role in glycolysis. The ever-expanding list of its functions has recently grown to include roles in subcellular compartments such as the mitochondria and extracellular milieu as well, all of which make PKM2 an attractive drug target in the pursuit of therapeutics for cancer.

Identification of PKM2 as a pyroptosis-related key gene aggravates senile osteoporosis via the NLRP3/Caspase-1/GSDMD signaling pathway

BACKGROUNDS

Senile osteoporosis-alternatively labeled as skeletal aging-encompasses age-induced bone deterioration and loss of bone microarchitecture. Recent studies have indicated a potential association between senile osteoporosis and chronic systemic inflammation, and pyroptosis in bone marrow-derived mesenchymal stem cells is speculated to contribute to bone loss and osteoporosis. Therefore, targeting pyroptosis in stem cells may be a potential therapeutic strategy for treating osteoporosis.

METHODS

Initially, we conducted bioinformatics analysis to screen the GEO databases to identify the key gene associated with pyroptosis in senile osteoporosis. Next, we analyzed the relationship between altered proteins and clinical data. In vitro experiments were then performed to explore whether the downregulation of PKM2 expression could inhibit pyroptosis. Additionally, an aging-related mouse model of osteoporosis was established to validate the efficacy of a PKM2 inhibitor in alleviating osteoporosis progression.

RESULTS

We identified PKM2 as a key gene implicated in pyroptosis in senile osteoporosis patients through bioinformatics analysis. Further analyses of bone marrow and stem cells demonstrated significant PKM2 overexpression in senile osteoporosis patients. Silencing PKM2 expression inhibited pyroptosis in senile stem cells, of which the osteogenesis potential and angiogenic function were also primarily promoted. Moreover, the results in vivo demonstrated that administering PKM2 inhibitors suppressed pyroptosis in senile osteoporosis mice and mitigated senile osteoporosis progression.

CONCLUSION

Our study uncovered PKM2, a key pyroptosis marker of bone marrow mesenchymal stem cells in senile osteoporosis. Shikonin, a PKM2 inhibitor, was then identified as a potential drug candidate for the treatment of osteoporosis.

Elevated plasma pyruvate kinase M2 concentrations are associated with the clinical severity and prognosis of coronary artery disease

Introduction

Pyruvate kinase M2 (PKM2) was involved in the pathophysiology of atherosclerosis and coronary artery disease (CAD). We tested whether plasma PKM2 concentrations were correlated with clinical severity and major adverse cardiovascular events (MACEs) in CAD patients.

Materials and methods

A total of 2443 CAD patients and 238 controls were enrolled. The follow-up time was two years. Plasma PKM2 concentrations were detected by enzyme-linked immunosorbent assay (ELISA) kits (Cloud-Clone, Wuhan, China) using SpectraMax i3x Multi-Mode Microplate Reader (Molecular Devices, San Jose, USA). The predictors of acute coronary syndrome (ACS) were assessed by logistic regression analysis. The association between PKM2 concentration in different quartiles and MACEs was evaluated by Kaplan-Meier (KM) curves with log-rank test and Cox proportional hazard models. The predictive value of PKM2 and a cluster of conventional risk factors was determined by Receiver operating characteristic (ROC) curves. The net reclassification improvement (NRI) and the integrated discrimination improvement (IDI) were utilized to evaluate the enhancement in risk prediction when PKM2 was added to a predictive model containing a cluster of conventional risk factors.

Results

In CAD patients, PKM2 concentration was the independent predictor of ACS (P < 0.001). Kaplan-Meier cumulative survival curves and Cox proportional hazards analyses revealed that patients with a higher PKM2 concentration had higher incidence of MACEs compared to those with a lower PKM2 concentration (P < 0.001). The addition of PKM2 to a cluster of conventional risk factors significantly increased its prognostic value of MACEs.

Conclusion

Baseline plasma PKM2 concentrations predict the clinical severity and prognosis of CAD.

Trichinella spiralis galectin binding to toll-like receptor 4 induces intestinal inflammation and mediates larval invasion of gut mucosa

Previous studies showed that Trichinella spiralis galectin (Tsgal) facilitates larval invasion of intestinal epithelium cells (IECs). However, IEC proteins binding with Tsgal were not identified, and the mechanism by which Tsgal promotes larval invasion is not clear. Toll-like receptors (TLRs) are protein receptors responsible for recognition of pathogens. The aim of this study was to investigate whether recombinant Tsgal (rTsgal) binds to TLR-4, activates inflammatory pathway in gut epithelium and mediates T. spiralis invasion. Indirect immunofluorescence (IIF), GST pull-down and co-immunoprecipitation (Co-IP) assays confirmed specific binding between rTsgal and TLR-4 in Caco-2 cells. qPCR and Western blotting showed that binding of rTsgal with TLR-4 up-regulated the TLR-4 transcription and expression in Caco-2 cells, and activated p-NF-κB p65 and p-ERK1/2. Activation of inflammatory pathway TLR-4/MAPK-NF-κB by rTsgal up-regulated pro-inflammatory cytokines (IL-1β and IL-6) and down-regulated anti-inflammatory cytokine TGF-β in Caco-2 cells, and induced intestinal inflammation. TAK-242 (TLR-4 inhibitor) and PDTC (NF-κB inhibitor) significantly inhibited the activation of TLR-4 and MAPK-NF-κB pathway. Moreover, the two inhibitors also inhibited IL-1β and IL-6 expression, and increased TGF-β expression in Caco-2 cells. In T. spiralis infected mice, the two inhibitors also inhibited the activation of TLR-4/MAPK-NF-κB pathway, ameliorated intestinal inflammation, impeded larval invasion of gut mucosa and reduced intestinal adult burdens. The results showed that rTsgal binding to TLR-4 in gut epithelium activated MAPK-NF-κB signaling pathway, induced the expression of TLR-4 and pro-inflammatory cytokines, and mediated larval invasion. Tsgal might be regarded as a candidate molecular target of vaccine against T. spiralis enteral invasive stage.

Role of glycolysis in inflammatory bowel disease and its associated colorectal cancer

Inflammatory bowel disease (IBD) has been referred to as the "green cancer," and its progression to colorectal cancer (CRC) poses a significant challenge for the medical community. A common factor in their development is glycolysis, a crucial metabolic mechanism of living organisms, which is also involved in other diseases. In IBD, glycolysis affects gastrointestinal components such as the intestinal microbiota, mucosal barrier function, and the immune system, including macrophages, dendritic cells, T cells, and neutrophils, while in CRC, it is linked to various pathways, such as phosphatidylinositol-3-kinase (PI3K)/AKT, AMP-activated protein kinase (AMPK), mammalian target of rapamycin (mTOR), and transcription factors such as p53, Hypoxia-inducible factor (HIF), and c-Myc. Thus, a comprehensive study of glycolysis is essential for a better understanding of the pathogenesis and therapeutic targets of both IBD and CRC. This paper reviews the role of glycolysis in diseases, particularly IBD and CRC, via its effects on the intestinal microbiota, immunity, barrier integrity, signaling pathways, transcription factors and some therapeutic strategies targeting glycolytic enzymes.

A Novel Serum Metabolomic Panel for the Diagnosis of Crohn's Disease

BACKGROUND

A distinctive metabolic phenotype provides the opportunity to discover noninvasive biomarkers for the diagnosis of Crohn's disease (CD) and for differentiating it from other intestinal inflammatory diseases. The study sought to identify new biomarkers for CD diagnosis.

METHODS

Serum metabolites from 68 newly diagnosed and treatment-naïve patients with CD and 56 healthy control (HC) subjects were profiled using targeted liquid chromatography-mass spectrometry. Five metabolic biomarkers were identified to distinguish patients with CD from the HC subjects and validated in a separate cohort consisting of 110 patients with CD and 90 HC subjects using a combination of univariate analysis, orthogonal partial least-squares discriminant analysis, and receiver-operating characteristic curve analysis. Differences in the 5 metabolites were evaluated among patients with CD and patients with ulcerative colitis (n = 62), intestinal tuberculosis (n = 48), and Behçet's disease (n = 31).

RESULTS

Among the 185 quantified metabolites, a panel of 5 (pyruvate, phenylacetylglutamine, isolithocholic acid, taurodeoxycholic acid, and glycolithocholic acid) were found to distinguish patients with CD with high accuracy from HC subjects, with an area under the curve of 0.861 (P < .001). The performance of the model in assessing clinical disease activity was comparable to that of the present biomarkers: C-reactive protein and erythrocyte sedimentation rate. The 5 metabolites were significantly different among the patients and were valuable in the differentiation between CD and other chronic intestinal inflammatory diseases.

CONCLUSIONS

The combination of 5 serum metabolite biomarkers for the diagnosis of CD has the potential to provide an accurate, noninvasive, and inexpensive alternative to conventional tests and might be valuable for the differentiation from other diagnostically challenging intestinal inflammatory diseases.

Changes of Serum Pyruvate Kinase M2 Level in Patients with Sepsis and Its Clinical Value

Purpose

The glucose metabolic reprogramming is an important pathological mechanism in sepsis, which involves a series of enzymes including Pyruvate kinase M2 (PKM2). The purpose of this study is to explore the diagnostic and prognostic value of serum PKM2 in sepsis patients.

Patients and Methods

This study recruited 143 sepsis patients, 91 non-sepsis patients, and 65 physical examiners, divided into sepsis group, non-sepsis group, and control group. Measure the serum PKM2 concentration of subjects, collect and analyze clinical and laboratory indicators of all subjects. Independent risk factors were selected by Logistic regression analysis. The area under curve (AUC) was calculated by plotting the receiver operating characteristic (ROC) curve to determine the diagnostic and prognostic value of biomarkers.

Results

Compared with non-sepsis and control groups, the serum PKM2 levels in the sepsis group were significantly increased (both P<0.001). PKM2 was an independent risk factor for sepsis and had the best diagnostic efficacy when combined with procalcitonin, with the AUC value of 0.9352. Patients with high levels of PKM2 were more likely to experience organ damage and had a higher incidence of septic shock. On the 1st and 3rd days of admission, the serum PKM2 levels in the septic shock group were higher than those in the sepsis group (both P<0.05), with AUC values of 0.7296 and 0.6247, respectively. On the 3rd and 7th days of admission, the serum PKM2 levels in the non-survival group were significantly higher than those in the survival group (both P<0.001), with AUC values of 0.7033 and 0.8732, respectively.

Conclusion

The serum PKM2 levels in sepsis patients are significantly increased and correlated with disease severity and clinical outcomes. PKM2 may be a new diagnostic and prognostic biomarker for sepsis.

The Role of hsa-miR-125b-5p Interaction with S1P/Ceramide Axis in the Potential Development of Inflammation-Associated Colon Cancer in Primary Sclerosing Cholangitis

Primary sclerosing cholangitis (PSC) is characterised by the co-occurrence of inflammatory bowel diseases, particularly ulcerative colitis (UC). We investigated how the interaction of miR-125b with the sphingosine-1-phosphate (S1P)/ceramide axis may predispose patients with PSC, PSC/UC, and UC to carcinogenesis in the ascending and sigmoid colons. The overexpression of miR-125b was accompanied by the upregulation of S1P, ceramide synthases, ceramide kinases, and the downregulation of AT-rich interaction domain 2 in the ascending colon of PSC/UC, which contributed to the progression of high microsatellite instability (MSI-H) colorectal carcinoma. We also showed that the overexpression of sphingosine kinase 2 (SPHK2) and the genes involved in the glycolytic pathway in the sigmoid colon of UC led to the upregulation of Interleukin 17 (IL-17). In vitro stimulation of human intestinal epithelial cells (Caco-2, HT-29, and NCM460D) with lipopolysaccharide suppressed miR-125b and increased proinflammatory cytokines, whereas the induction of miR-125b activity by either a miR-125b mimetic or lithocholic acid resulted in the inhibition of miR-125b targets. In summary, miR-125b overexpression was associated with an imbalance in the S1P/ceramide axis that can lead to MSI-H cancer progression in PSC/UC. Furthermore, SPHK2 overexpression and a change in the cellular metabolic flux are important players in inflammation-associated colon cancer in UC.

Increased stromal PFKFB3-mediated glycolysis in inflammatory bowel disease contributes to intestinal inflammation

Inflammatory bowel disease (IBD) is a chronic relapsing inflammation of the intestinal tract with currently not well-understood pathogenesis. In addition to the involvement of immune cells, increasing studies show an important role for fibroblasts in the pathogenesis of IBD. Previous work showed that glycolysis is the preferred energy source for fibroblasts in fibrotic diseases. 6-phosphofructo-2-kinase/fructose-2, 6-bisphosphatase 3 (PFKFB3) is a key kinase supporting glycolysis. Increased expression of PFKFB3 in several cancers and inflammatory diseases has been previously reported, but the metabolic status of fibroblasts and the role of PFKFB3 in patients with IBD are currently unknown. Therefore, in this study, we evaluated the role of glycolysis and PFKFB3 expression in IBD. Single-sample gene set enrichment analysis (ssGSEA) revealed that glycolysis was significantly higher in IBD intestinal samples, compared to healthy controls, which was confirmed in the validation cohorts of IBD patients. Single-cell sequencing data indicated that PFKFB3 expression was higher in IBD-derived stromal cells. In vitro, PFKFB3 expression in IBD-derived fibroblasts was increased after the stimulation with pro-inflammatory cytokines. Using seahorse real-time cell metabolic analysis, inflamed fibroblasts were shown to have a higher extracellular acidification rate and a lower oxygen consumption rate, which could be reversed by inhibition of JAK/STAT pathway. Furthermore, increased expression of pro-inflammatory cytokines and chemokines in fibroblasts could be reverted by PFK15, a specific inhibitor of PFKFB3. In vivo experiments showed that PFK15 reduced the severity of dextran sulfate sodium (DSS)- and Tcell transfer induced colitis, which was accompanied by a reduction in immune cell infiltration in the intestines. These findings suggest that increased stromal PFKFB3 expression contributes to inflammation and the pathological function of fibroblasts in IBD. Inhibition of PFKFB3 suppressed their inflammatory characteristics.

The crosstalk between NLRP3 inflammasome and gut microbiome in atherosclerosis

Atherosclerosis (AS) is chronic pathological process based on the inflammatory reaction associated with factors including vascular endothelial dysfunction, inflammation, and autoimmunity. Inflammasomes are known to be at the core of the inflammatory response. As a pattern recognition receptor of innate immunity, the NLRP3 inflammasome mediates the secretion of inflammatory factors by activating the Caspase-1, which is important for maintaining the immune system and regulating the gut microbiome, and participates in the occurrence and development of AS. The intestinal microecology is composed of a large number of complex structures of gut microbiota and its metabolites, which play an important role in AS. The gut microbiota and its metabolites regulate the activation of the NLRP3 inflammasome. Targeting the NLRP3 inflammasome and regulating intestinal microecology represent a new direction for the treatment of AS. This paper systematically reviews the interaction between the NLRP3 inflammasome and gut microbiome in AS, strategies for targeting the NLRP3 inflammasome and gut microbiome for the treatment of AS, and provides new ideas for the research and development of drugs for the treatment of AS.

Podocyte specific deletion of PKM2 ameliorates LPS-induced podocyte injury through beta-catenin

BACKGROUND

Acute kidney injury (AKI) is associated with a severe decline in kidney function caused by abnormalities within the podocytes' glomerular matrix. Recently, AKI has been linked to alterations in glycolysis and the activity of glycolytic enzymes, including pyruvate kinase M2 (PKM2). However, the contribution of this enzyme to AKI remains largely unexplored.

METHODS

Cre-loxP technology was used to examine the effects of PKM2 specific deletion in podocytes on the activation status of key signaling pathways involved in the pathophysiology of AKI by lipopolysaccharides (LPS). In addition, we used lentiviral shRNA to generate murine podocytes deficient in PKM2 and investigated the molecular mechanisms mediating PKM2 actions in vitro.

RESULTS

Specific PKM2 deletion in podocytes ameliorated LPS-induced protein excretion and alleviated LPS-induced alterations in blood urea nitrogen and serum albumin levels. In addition, PKM2 deletion in podocytes alleviated LPS-induced structural and morphological alterations to the tubules and to the brush borders. At the molecular level, PKM2 deficiency in podocytes suppressed LPS-induced inflammation and apoptosis. In vitro, PKM2 knockdown in murine podocytes diminished LPS-induced apoptosis. These effects were concomitant with a reduction in LPS-induced activation of β-catenin and the loss of Wilms' Tumor 1 (WT1) and nephrin. Notably, the overexpression of a constitutively active mutant of β-catenin abolished the protective effect of PKM2 knockdown. Conversely, PKM2 knockdown cells reconstituted with the phosphotyrosine binding-deficient PKM2 mutant (K433E) recapitulated the effect of PKM2 depletion on LPS-induced apoptosis, β-catenin activation, and reduction in WT1 expression.

CONCLUSIONS

Taken together, our data demonstrates that PKM2 plays a key role in podocyte injury and suggests that targetting PKM2 in podocytes could serve as a promising therapeutic strategy for AKI.

TRIAL REGISTRATION

Not applicable. Video abstract.

Extracellular pyruvate kinase M2 promotes osteoclastogenesis and is associated with radiographic progression in early rheumatoid arthritis

Extracellular PKM2 (exPKM2) levels have been reported to be increased in several cancers and inflammatory diseases, including rheumatoid arthritis (RA). This study aimed to investigate the association of circulating exPKM2 levels with radiographic progression in RA patients and the effect of exPKM2 on osteoclastogenesis. Plasma and synovial fluid exPKM2 levels were significantly elevated in RA patients. Plasma exPKM2 levels were correlated with RA disease activity and were an independent predictor for radiographic progression in RA patients with a disease duration of ≤ 12 months. CD14⁺ monocytes but not RA fibroblast-like synoviocytes secreted PKM2 upon stimulation with inflammatory mediators. Recombinant PKM2 (rPKM2) increased the formation of tartrate-resistant acid phosphatase (TRAP)-positive multinuclear cells and resorption pit in osteoclast precursors, dose-dependently, even in the absence of receptor activator of nuclear factor-kappa B ligand (RANKL). rPKM2 treatment upregulated the expression of dendrocyte-expressed seven transmembrane protein (DC-STAMP) and MMP-9 via the ERK pathway. Although rPKM2 did not directly bind to RAW264.7 cells, extracellular application of pyruvate, the end-product of PKM2, showed effects similar to those seen in rPKM2-induced osteoclastogenesis. These results suggest that exPKM2 is a potential regulator of RA-related joint damage and a novel biomarker for subsequent radiographic progression in patients with early-stage RA.

Targeting Immune Cell Metabolism in the Treatment of Inflammatory Bowel Disease

The cells of the immune system are highly dynamic, constantly sensing and adapting to changes in their surroundings. Complex metabolic pathways govern leukocytes' ability to fine-tune their responses to external threats. Mammalian target of rapamycin complex 1 and hypoxia inducible factor are important hubs of these pathways and play a critical role coordinating cell activation and proliferation and cytokine production. For this reason, these molecules are attractive therapeutic targets in inflammatory disease. Insight into perturbations in immune cell metabolic pathways and their impact on inflammatory bowel disease (IBD) progression are starting to emerge. However, it remains to be determined whether the aberrations in immune metabolism that occur in gut resident immune cells contribute to disease pathogenesis or are reflected in the peripheral blood of patients with IBD. In this review, we explore what is known about the metabolic profile of T cells, monocytes, macrophages, dendritic cells, and natural killer cells in IBD and discuss the potential of manipulating immune cell metabolism as a novel approach to treating IBD.

Pyruvate kinase M2 in chronic inflammations: a potpourri of crucial protein-protein interactions

Chronic inflammation (CI) is a primary contributing factor involved in multiple diseases like cancer, stroke, diabetes, Alzheimer's disease, allergy, asthma, autoimmune diseases, coeliac disease, glomerulonephritis, sepsis, hepatitis, inflammatory bowel disease, reperfusion injury, and transplant rejections. Despite several expansions in our understanding of inflammatory disorders and their mediators, it seems clear that numerous proteins participate in the onset of CI. One crucial protein pyruvate kinase M2 (PKM2) much studied in cancer is also found to be inextricably woven in the onset of several CI's. It has been found that PKM2 plays a significant role in several disorders using a network of proteins that interact in multiple ways. For instance, PKM2 forms a close association with epidermal growth factor receptors (EGFRs) for uncontrolled growth and proliferation of tumor cells. In neurodegeneration, PKM2 interacts with apurinic/apyrimidinic endodeoxyribonuclease 1 (APE1) to onset Alzheimer's disease pathogenesis. The cross-talk of protein tyrosine phosphatase 1B (PTP1B) and PKM2 acts as stepping stones for the commencement of diabetes. Perhaps PKM2 stores the potential to unlock the pathophysiology of several diseases. Here we provide an overview of the notoriously convoluted biology of CI's and PKM2. The cross-talk of PKM2 with several proteins involved in stroke, Alzheimer's, cancer, and other diseases has also been discussed. We believe that considering the importance of PKM2 in inflammation-related diseases, new options for treating various disorders with the development of more selective agents targeting PKM2 may appear.

Serum complement C3 and α2-macroglobulin are potentially useful biomarkers for inflammatory bowel disease patients

Aims

Ulcerative colitis (UC), characterized by chronic inflammation and its recurrence in the large intestine, is well known as inflammatory bowel disease (IBD). Suitable biomarkers specific for UC are poorly understood till date. We aimed to discover novel serum biomarkers for UC and identify good indicators that reflected the severity of UC.

Main methods

Serum samples were obtained from out-patients with IBD (n = 101) and healthy volunteers (HVs, n = 101). Serum proteins were subjected to high performance liquid chromatography (HPLC) and sodium dodecyl sulfate-electrophoresis (SDS-PAGE) analysis. After electrophoresis, proteins in the gel were identified by mass spectrometry. Further, the protein concentration was measured by enzyme-linked immunosorbent assays (ELISAs). Based on the results, correlations between the serum levels of these proteins and the disease activity index scores for UC were statistically evaluated.

Principal findings

HPLC showed that chromatograms of serum proteins from HVs apparently differed from those of patients with IBD. Eleven protein bands, which were different in their protein concentrations from those in HVs, were separated by SDS-PAGE accordingly. Among them, complement C3 (c-C3) and α₂-macroglobulin (α₂-MG), with high protein scores, were identified by mass spectrometry. The serum concentration of c-C3 in patients with IBD was higher than that in HVs. However, the level of α₂-MG in patients with IBD was significantly lower than that in HVs. Hence, the serum levels of c-C3 and α₂-MG could be good indicators of the severity of UC.

Conclusion

Serum c-C3 and α₂-MG are suitable biomarkers for monitoring the condition of patients with UC.

Iridin Prevented Against Lipopolysaccharide-Induced Inflammatory Responses of Macrophages via Inactivation of PKM2-Mediated Glycolytic Pathways

Purpose

Abnormal glycolysis of immune cells contributed to the development of inflammatory response. Inhibition of this Warburg phenotype could be a promising strategy for preventing various inflammatory diseases. Iridin (IRD) is a natural isoflavone, and exerts anticancer, antioxidant, and anti-inflammatory effects. However, the underlying mechanism of IRD on acute inflammation remains unknown. In this study, the protective effects of IRD against lipopolysaccharide (LPS)-induced inflammation were investigated in murine macrophage RAW264.7 cells and in mice.

Methods

The inhibition of IRD on NO production in culture medium was detected by Griess assay while the levels of TNF-α, IL-1β, and MCP-1 were detected by ELISA assay. The effects of IRD on OCR and ECAR levels in LPS-treated macrophages were monitored by using Seahorse Analyzer. The apoptosis rate as well as the release of ROS and NO of RAW264.7 cells were analyzed by flow cytometric assay. The protective effects of IRD were investigated on LPS-induced inflammation in mice. The expressions of PKM2 and its downstream (p-JAK1, p-STAT1, p-STAT3, p-p65, iNOS, and COX2) in cells and in lung tissues were detected by Western blotting analysis.

Results

IRD treatment at the concentrations of 12.5-50 μM significantly inhibited the productions of TNF-α, IL-1β, MCP-1, and ROS, and suppressed the levels of glucose uptake and lactic acid in LPS-treated RAW264.7 cells. Oral administration with IRD (20-80 mg/kg) inhibited LPS-induced acute lung injury as well as inflammatory cytokine production in mice. Moreover, IRD targeted pyruvate kinase isozyme type M2 (PKM2) and suppressed its downstream p-JAK1, p-STAT1, p-STAT3, p-p65, iNOS, and COX2, which could be abolished by PKM2 agonist DASA-58 and antioxidant N-acetyl-L-cysteine, but partly be reversed by NF-κB activator CUT129 and JAK1 activator RO8191.

Conclusion

IRD alleviated LPS-induced inflammation through suppressing PKM2-mediated pathways, and could be a potential candidate for the prevention of inflammatory diseases.

The Role of PKM2 in Metabolic Reprogramming: Insights into the Regulatory Roles of Non-Coding RNAs

Pyruvate kinase is a key regulator in glycolysis through the conversion of phosphoenolpyruvate (PEP) into pyruvate. Pyruvate kinase exists in various isoforms that can exhibit diverse biological functions and outcomes. The pyruvate kinase isoenzyme type M2 (PKM2) controls cell progression and survival through the regulation of key signaling pathways. In cancer cells, the dimer form of PKM2 predominates and plays an integral role in cancer metabolism. This predominance of the inactive dimeric form promotes the accumulation of phosphometabolites, allowing cancer cells to engage in high levels of synthetic processing to enhance their proliferative capacity. PKM2 has been recognized for its role in regulating gene expression and transcription factors critical for health and disease. This role enables PKM2 to exert profound regulatory effects that promote cancer cell metabolism, proliferation, and migration. In addition to its role in cancer, PKM2 regulates aspects essential to cellular homeostasis in non-cancer tissues and, in some cases, promotes tissue-specific pathways in health and diseases. In pursuit of understanding the diverse tissue-specific roles of PKM2, investigations targeting tissues such as the kidney, liver, adipose, and pancreas have been conducted. Findings from these studies enhance our understanding of PKM2 functions in various diseases beyond cancer. Therefore, there is substantial interest in PKM2 modulation as a potential therapeutic target for the treatment of multiple conditions. Indeed, a vast plethora of research has focused on identifying therapeutic strategies for targeting PKM2. Recently, targeting PKM2 through its regulatory microRNAs, long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs) has gathered increasing interest. Thus, the goal of this review is to highlight recent advancements in PKM2 research, with a focus on PKM2 regulatory microRNAs and lncRNAs and their subsequent physiological significance.

Gene Regulatory Effect of Pyruvate Kinase M2 is Involved in Renal Inflammation in Type 2 Diabetic Nephropathy

BACKGROUND AND AIMS

The inflammation of glomerular endothelial cells induces and promotes the activation of macrophages and contributes to the development of diabetic nephropathy. Thus, this study aimed to investigate the gene regulatory effect and potential role of pyruvate kinase M2 (PKM2) in inflammatory response in diabetic nephropathy.

METHODS

The plasma PKM2 levels of patients with diabetes were evaluated. Eight-week-old mice were divided into three groups (WT, db/db mice, and db/db mice treated with TEPP-46) and raised for 12 weeks. Blood and kidney samples were collected at the end of the experiment. Endothelial cells were stimulated with high glucose with or without TEPP-46. The expression of intercellular adhesion molecule 1 (ICAM-1), interleukin 6 (IL-6), interleukin 1 beta (IL-1β), phospho-PKM2, PKM2, phospho-STAT3(signal transducer and activator of transcription), STAT3, nuclear factor kappa B (NF-kB), and phospho-NF-kB in vivo and in vitro were determined using Western blot. The activation of macrophages (CD68+CD86+) in the glomeruli was assessed via fluorescent double staining. Moreover, immune endothelial adhesion experiments were performed.

RESULTS

The plasma PKM2 levels of patients with type 2 diabetes increased. P-PKM2 was up-regulated in vivo and in vitro. TEPP-46 decreased inflammatory cell infiltration and ICAM-1 expression in vivo and in vitro and inhibited the differentiation of macrophages to M1 cells in db/db mice with diabetic nephropathy. PKM2 regulated the phosphorylation of STAT3 and NF-kB. Furthermore, high glucose levels induced the transition from tetramer to dimer and the nuclear translocation of PKM2.

CONCLUSION

The gene regulatory effect of PKM2 is involved in renal inflammation in type 2 diabetic nephropathy by promoting the phosphorylation of STAT3 and NF-kB and the expression of intercellular adhesion molecule 1. Thus, the down-regulation of phosphorylated PKM2 may have protective effects against diabetic nephropathy by inhibiting renal inflammation.

RNA-binding protein NONO contributes to cancer cell growth and confers drug resistance as a theranostic target in TNBC

Breast cancer (BC) is one of the most common cancers in women. TNBC (Triple-negative breast cancer) has limited treatment options and still lacks viable molecular targets, leading to poor outcomes. Recently, RNA-binding proteins (RBPs) have been shown to play crucial roles in human cancers, including BC, by modulating a number of oncogenic phenotypes. This suggests that RBPs represent potential molecular targets for BC therapy.

Methods: We employed genomic data to identify RBPs specifically expressed in TNBC. NONO was silenced in TNBC cell lines to examine cell growth, colony formation, invasion, and migration. Gene expression profiles in NONO-silenced cells were generated and analyzed. A high-throughput screening for NONO-targeted drugs was performed using an FDA-approved library.

Results: We found that the NONO RBP is highly expressed in TNBC and is associated with poor patient outcomes. NONO binds to STAT3 mRNA, increasing STAT3 mRNA levels in TNBC. Surprisingly, NONO directly interacts with STAT3 protein increasing its stability and transcriptional activity, thus contributing to its oncogenic function. Importantly, high-throughput drug screening revealed that auranofin is a potential NONO inhibitor and inhibits cell growth in TNBC.

Conclusions: NONO is an RBP upstream regulator of both STAT3 RNA and protein levels and function. It represents an important and clinically relevant promoter of growth and resistance of TNBCs. NONO is also therefore a potential therapeutic target in TNBC.

Intestinal epithelial PKM2 serves as a safeguard against experimental colitis via activating β-catenin signaling

The pyruvate kinase M2 (PKM2)-mediated aerobic glycolysis has been shown to play a critical role in promoting cell survival and proliferation. However, little is known about the function of intestinal epithelial PKM2 in intestine homeostasis. Here we investigate whether and how intestinal epithelial PKM2 modulates the morphology and function of the adult intestine in experimental colitis. Analyzing colonoscopic biopsies from Crohn's disease and ulcerative colitis patients, we found significantly decreased level of intestinal epithelial PKM2 in patients compared to that in non-inflamed tissues. Similar reduction of intestinal epithelial PKM2 was observed in mice with dextran sulfate sodium-induced colitis. Moreover, intestinal epithelial-specific PKM2-knockout (Pkm2-/-) mice displayed more severe intestinal inflammation, as evidenced by a shortened colon, disruption of epithelial tight junctions, an increase in inflammatory cytokine levels, and immune cell infiltration, when compared to wild-type mice. Gene profiling, western blot, and function analyses indicated that cell survival signals, particularly the Wnt/β-catenin pathways, were associated with PKM2 activity. Increasing mouse intestinal epithelial PKM2 expression via delivery of a PKM2-expressing plasmid attenuated experimental colitis. In conclusion, our studies demonstrate that intestinal epithelial PKM2 increases cell survival and wound healing under the colitic condition via activating the Wnt/β-catenin signaling.

Pyruvate kinase M2: A simple molecule with complex functions

Pyruvate kinase M2 is a critical enzyme that regulates cell metabolism and growth under different physiological conditions. In its metabolic role, pyruvate kinase M2 catalyzes the last glycolytic step which converts phosphoenolpyruvate to pyruvate with the generation of ATP. Beyond this metabolic role in glycolysis, PKM2 regulates gene expression in the nucleus, phosphorylates several essential proteins that regulate major cell signaling pathways, and contribute to the redox homeostasis of cancer cells. The expression of PKM2 has been demonstrated to be significantly elevated in several types of cancer, and the overall inflammatory response. The unusual pattern of PKM2 expression inspired scientists to investigate the unrevealed functions of PKM2 and the therapeutic potential of targeting PKM2 in cancer and other disorders. Therefore, the purpose of this review is to discuss the mechanistic and therapeutic potential of targeting PKM2 with the focus on cancer metabolism, redox homeostasis, inflammation, and metabolic disorders. This review highlights and provides insight into the metabolic and non-metabolic functions of PKM2 and its relevant association with health and disease.

Loss of PKM2 in Lgr5+ intestinal stem cells promotes colitis-associated colorectal cancer

The regulatory properties of pyruvate kinase M2 isoform (PKM2), the key glycolytic enzyme, influence altered energy metabolism including glycolysis in cancer. In this study, we found that PKM2 was highly expressed in patients with ulcerative colitis or colorectal cancer (CRC). We then investigated the effectiveness of conditionally ablating PKM2 in Lgr5+ intestinal stem cells (ISC) using a mouse model of colitis-associated CRC (AOM plus DSS). Tamoxifen-inducible Lgr5-driven deletion of PKM2 in ISC (PKM2ΔLgr5-Tx) significantly promoted tumor incidence and size in the colon and lower body weight compared with findings in vehicle-treated mice (PKM2ΔLgr5-Veh). Histopathologic analysis revealed considerable high-grade dysplasia and adenocarcinoma in the colon of PKM2ΔLgr5-Tx mice while PKM2ΔLgr5-Veh mice had low- and high-grade dysplasia. Loss of PKM2 was associated with dominant expression of PKM1 in Lgr5+ ISC and their progeny cells. Further, the organoid-forming efficiency of whole cancer cells or Lgr5+ cells obtained from colon polyps of PKM2ΔLgr5-Tx mice was significantly increased when compared with PKM2ΔLgr5-Veh mice. Cancer organoids from PKM2ΔLgr5-Tx mice exhibited increased mitochondrial oxygen consumption and a shift of metabolites involved in energy metabolism. These findings suggest that loss of PKM2 function in ISC promotes colitis-associated CRC.

Use of biomarkers in inflammatory bowel disease

There are many useful biomarkers for initial diagnosis and the management of inflammatory bowel disease. Serologic biomarkers have been traditionally used because they are widely disposable, but recently faecal biomarkers, especially faecal calprotectin, have acquired great importance as they have shown to be more precise when establishing suspicion of the disease and also as predictors of mucosal healing or persistence of inflammatory activity. Faecal calprotectin is a good tool for predicting abnormal endoscopic studies, but has limited specificity because its levels can be altered in many digestive diseases presenting with similar symptoms. The precision of faecal calprotectin is higher when associated with other altered parameters, especially with C-reactive protein, or with clinical scores of inflammatory activity. Finally, there are many new generation serologic and faecal biomarkers. Despite there not being much evidence about these yet, some of them have shown promising results in different studies.